Trim.
You clearly heard a different version of events than I did.
Did anyone explain to you how two sigs corporals in a private car stood out in an ordinary street after making a bad choice on their 'orientation' route, that had not been preplanned?
The Lynx was there to film the crowd, and would have had no idea that the two corporals were heading that way. Was it also explained to you why (if the crew knew who the car's occupants were) two British service men were allowed to be murdered over quite a long period of time with no attempted intervention (attempted being the correct word)!
From memory, there were not that many variations in SOP's at that time (mainly for black/green ops), and just sitting back while someone is committing a violent life threatening act didn't really feature too heavily. On a day to day basis is was not uncommon for the last member of a brick to be pulled into a house for a bit of a kicking, and the SOP (official or otherwise) wasn't to simply leave them to it!
Just my two penneth.